1. Field of the Invention
The present invention relates to a useful method of joining together end portions of superposed members. In particular, the present invention relates to a method of joining together superposed members, in which a plurality of members to be joined together are piled on one another and the members are joined together with one another at the end portions thereof.
2. Discussion of Related Art
There have been methods of joining together a plurality of members to be joined together with one another, at the end portions thereof, as forms of joining together superposed parts of the plurality of members, and these methods are known as butt-joint, edge-welding, and so on.
There is generally considered adopting a fusion welding, in which an arc or a laser is used, in order to join together the end portions of the superposed parts. However, in this case, there is an inherent problem of causing a joint defect caused by a void etc., in addition to an adverse influence to the other sections of the members caused by the welding. Moreover, if a thickness of the superposed parts of the members to be joined together isn't thick enough, there is caused a problem of burn-through. Therefore, it has been difficult to obtain an advantageous and sound joint structure.
Unlike a method of joining which involves a generation of a large amount of heat (energy) such as the above-mentioned fusion welding, there is also known a friction stir welding, in which a friction heating is generated between two members to be joined together. In the method of the friction stir welding: the members to be joined together are held in abutting contact with end faces of each other; a rotary tool is pressed to the abutting end faces of the members while the rotary tool is rotated relative to the members; and the members are subjected to a pressure weld making use of the friction heating generated at the interface between the members and the rotary tool. Accordingly, the rotary tool needs to be rotated while the members to be joined together are held in butting contact with each other, and therefore, it is impossible to join together the above-mentioned superposed parts of the plurality of members at the end portions thereof Moreover, when this method of fusion welding is applied, it is difficult to avoid generating largely curled burrs, so that a shape or an appearance of the joint portion is unsatisfactory.
The present invention has been made in the light of the situations described above. It is therefore an object of the invention to provide a novel method that enables to effectively join together end portions of superposed parts of members to be joined together, without adopting a fusion welding method. It is also an object of the invention to provide a method that enables to easily and stably join together the end portions of the superposed parts of the members, even if the superposed parts are thin.
The object indicated above may be achieved according to a principle of the present invention, which provides a method of joining a plurality of members to be joined together, by piling the plurality of members on one another and joining together the members with one another at end portions of superposed parts of the members, characterized in that the superposed parts of the members are held by restraining the superposed parts from both sides thereof, while a pressing tool, which is harder than the members, is pressed to end faces, which are some sections of the end portions, of the superposed parts and the pressing tool is rotated and/or moved relative to the superposed parts, so that the end faces of the superposed parts are rubbed to cause a friction heating which leads to a plastic flow, whereby the plurality of the members are joined together at the end portions of the superposed parts thereof.
In the method of joining together the end portions of the superposed members according to the present invention, the superposed parts of the members are held by restraining the superposed parts from both sides thereof, while a pressing tool, which is harder than the members, is pressed to the end faces of the superposed parts and the pressing tool is rotated and/or moved relative to the superposed parts, so that the end faces of the superposed parts are rubbed to cause a friction heating which results in softening the end portions which leads to a plastic flow, whereby the plurality of the members are effectively joined together under solid phase at the end portions of the superposed parts thereof According to the present method, problems resulting from the fusion welding are wholly solved, and an effective joining at the intended end portions or end surface layer is realized.
In addition, in the method according to the present invention, there is only required an operation of relatively rotating/moving the pressing tool, while the pressing tool is pressed to the end faces of the superposed parts. Accordingly, there can be simplified a structure of a joining device, without requiring expensive welding devices or auxiliary machines etc., and there can also be simplified joining operations. Accordingly, in addition to the simplification of the joining operation, there can be advantageously distributed to reduce a cost of the welding.
In order to achieve the above-mentioned objects and other objects recognized by overall the description of this specification and the attached drawings, the present invention is preferably practiced in at least the following features. The present invention may also be embodied by suitably combining the undermentioned features. It is to be understood that the embodiments and the technical features of the present invention are not limited to the followings, but may be recognized based on the overall description of this specification and the inventions disclosed in the attached drawings.